Sunset Hill Middle School is surrounded by old-fashioned open communities and a large farmers' market, and is densely populated and has a relatively complex population profile. The Tianhe community, where the victim Xu Zilin lived, was located at the southern end of the school, about 1.4 kilometers apart. From 2014 to the eve of the crime, Xu Zilin has been running a small stall selling egg scones near the main entrance of the school, living a simple life of two points and one line every day, never holding grudges with anyone, and no suspected perpetrators have been found around him.

Walking back and forth around the school gate of Xishan Middle School, Gu Song and Huo Yan returned to the roadside where Xu Zilin ran a stall before his death. Here you can see the school building, under the quiet night, the rows of neat windows shine with warm and bright lights, and you can see the books stacked high by the window and the hard-working figures of the students.

Xu Zilin looks at such a scene every day, and maybe he often thinks of his son who is far away sitting in the classroom and preparing for the college entrance examination. However, he would never have imagined that he could not wait for the day when his son grew up to die in such a cruel way.

"I think it's possible that the killer met the victim here." Huo Yan stood on the side of the road, contemplating, imagining that she was the vendor who sold egg scones. "My life is simple, and relationships can be sorted out with two hands. I never get into trouble, whether it's my neighbors or other vendors, I get along with them. I never noticed that anyone showed ill will towards me, nor did I think that the simple, ordinary, honest, and kind me would be the object of someone's desire to kill. On weekdays, the people I come into contact with the most are none other than the residents living in the neighborhood and the teachers and students of Yushan Middle School, but I have no grievances with them, and I can't imagine that one of these people is the murderer of me......"

Huo Yan said these words to herself, and asked Gu Song in an inquiring tone, "You say, is it possible that the murderer chose Xu Zilin as a target here, and even bought something in front of his stall?" ”

"There is indeed such a possibility, because the main way for Xu Zilin to contact the outside world is the small business he carefully manages. But......" Gu Song looked at Huo Yan suspiciously and asked, "What about the motive for the crime?" The murderer killed a beautiful 24-year-old girl for the first time, but chose a 47-year-old uncle who sold egg scones for the second time, and there was no connection or common ground between the two, and I didn't understand the murderer's method of selecting victims. ”

"You're right." Huo Yan sighed and shook her head, although she had just taken over this case for less than two hours, she already felt a little powerless. It seems that researching theories and teaching are the same thing, but actually participating in solving cases is not a level of difficulty.

Thinking about his father's achievements in this life and the cases he successfully solved using psychological portraits, Huo Yan knew that she still had too much to learn. If it weren't for the fact that her father was seriously ill and could no longer assist the public security organs in handling the case, how could Xia Shi give her such a tricky job?

Sure enough, it was stained with her father's light, Huo Yan smiled self-deprecatingly. She understands that she has been committed to theoretical research lacks practical experience and has many deficiencies in ability, but her father's unfulfilled wish and the great cause that she has never forgotten can be accomplished by no one except herself.

After a moment of silence, Huo Yan regained her spirits, her eyes shining with brilliance. "Perhaps, we can try to infer the murderer's motive from his unique criminal mark. In both cases, the killer used four steel nails to penetrate the victim's lips, which shows that this marking act is of great significance to the murderer.

"You have discussed this issue many times before, and you believe that the reason why the murderer wanted to shut the victim's mouth was to prevent the victim from speaking, and although the victim had been stabbed to death before committing this act, in the eyes of the murderer, perhaps only by doing so could he feel completely reassured. Since we can't find out what the two victims have in common on the surface, is it possible that both victims had a verbal conflict with the murderer before their deaths, which stimulated the murderer's desire to kill. It is even possible that the victim simply inadvertently said something that disgusted the murderer, thus triggering the tragedy. ”

"If that's the case, the murderer must be a psychologically abnormal pervert, otherwise how could a normal person kill someone because of a few words, and more than one." Gu Song thought for a moment, and suddenly frowned. "But there is one thing that is strange, and it may become a breakthrough in the case."

"Oh? What is it? ”

"As you just said, the murderer may have met Xu Zilin at the stall here and selected him as a target. And what about He Yao, the victim of the first case? On what occasion did the killer come into contact with her and make up his mind to kill her? ”

"Could it be a place to work? Otherwise......" Huo Yan thought about it, and quickly gave up her rambling speculation, "No, He Yao's social circle is relatively extensive, and his life trajectory is relatively rich, so there are too many possibilities to contact the murderer......"

"Teacher Huo, you have overlooked a very critical issue." Gu Song reminded in time, "He Yao is different from Xu Zilin, she was killed in her own home. According to the results of the visit, we learned that at about 9 o'clock in the evening of September 16, a man knocked on the door of He Yao's house, and that person was probably the murderer we were looking for.

"Suppose that person killed He Yao, he entered the crime scene peacefully, and at first did not arouse the victim's vigilance, but then, he brutally killed He Yao with a murder weapon taken from the spot, which is a bit like a temporary crime no matter how you look at it. As for the steel nails that represented special meanings, we initially speculated that they were items carried by the murderer, but after thinking about it carefully, I did not rule out the possibility that the murderer could return to the scene of the crime again and continue to commit the crime.

"Based on the above situation, I think there is still a certain social connection between the murderer and He Yao, but the relationship between them may not be so close, so the police omitted some characters and information in the process of investigation. When it comes to solving a serial murder case, the first case is often the most important and the one that can provide us with the most information.

"If killing He Yao is a fuse, successfully igniting the murderer's desire to kill that has been hidden for many years, and helping him cross the insurmountable barrier of life and death, the crime in the future will only become easier and easier. From acquaintances to strangers, from crimes of passion to premeditated murder, everything will slowly become logical and natural, including the next crime......"

Huo Yan watched Gu Song say this inference in surprise, and was already convinced of his so-called "detective" identity. Although the two of them had only been in contact for a few hours, she believed that she had been completely "attracted" to this mysterious man, and wanted to know more about him, get close to him, and even study him.

Yes, this man's life experience must be very complicated, although he is not yet thirty years old this year, but his deep and charming eyes are full of joys and sorrows. The cases he has participated in, and the gangsters he has personally subdued, are all good materials worth studying and learning.

Seeing Huo Yan looking at herself without saying a word, and didn't speak for a long time, Gu Song felt a little uncomfortable. In order to alleviate the embarrassment, he pointed to the northeast direction of Xishan Middle School and said to Huo Yan: "Let's go, let's go to the crime scene of the first case by the way to see the situation, although I have already been there once during the day, but you should want to go there to have a look now." ”

"Okay, then I'll let you lead the way." Huo Yan said politely.

The two of them got into the car, Huo Yan took out the area map, looked at the red markers on it and said: "The Ganges community is located in the northeast of Xishan Middle School, and the shortest straight-line distance from Tianhe community is about 3.2 kilometers. Judging from the current situation, the murderer's range of activities is relatively concentrated, and it cannot be ruled out that he lived in this area, but it is still a bit hasty to make a judgment based on only the two cases that have occurred so far. ”

"Not necessarily." Gu Song leaned over, moved a little closer to Huo Yan, and pointed at the Xishan Middle School on the map with his index finger, "If the murderer intersected with Xu Zilin in this place, it means that his range of activities will not be too far from here." Even if he doesn't live nearby, he should work nearby. For example......" he pointed to the surrounding farmers' markets and schools, as well as some scattered shops in the surrounding area.

"Kind of makes sense." Huo Yan circled an approximate radius of movement on the map with a marker, and frowned as she looked at it. "This area of old-fashioned residential areas is too dense, and there are a lot of migrant workers, so the task of investigation is very heavy."

"But with a height of 1.73 to 1.78 meters, there are not many men who can relate to He Yao."

"That's right." Huo Yan nodded approvingly, and then added, "Based on the current information, I believe that the murderer's age should not be too big, and the preliminary inference should not be more than 35 years old." He is not highly educated, has a modest income, and may be engaged in manual or technical jobs. His personality should be a more introverted type, not very talkative, not a wide range of friends, and his psychological quality is relatively fragile.

"He's had a rough life, failures or unfair treatment. Because of the lack of channels to vent negative emotions, he has lived in depression for a long time. When this emotion is beyond his ability to tolerate, it will completely explode at the prompting of a chance event. Although he usually comes across as silent and honest, he may not be good at controlling his emotions and will appear angry and irritable in some cases. After Huo Yan finished speaking, she looked at Gu Song with expectant eyes, "I can only think of so much for the time being, and some places may still need to be corrected." Officer Gu, do you have anything to add? ”

"Well, let me think about it......" Gu Song stared at the night outside the car window, and said after a moment of silence, "The murderer stabbed the victim frantically dozens of times, each of which was so crisp and hard, if he didn't have any deep hatred with the victim, and maybe even didn't know each other at all, why did he act so angry when he committed the crime?" It's like a mad beast. I have the feeling that there may be something wrong with the murderer's mental condition, for example, could he have some kind of paranoid delusion? Unauthorized exaggeration and distortion of certain objective facts? ”

"It's a possibility." Huo Yan said approvingly, "Maybe it's this mental disorder that makes his behavior unreasonable, and at the same time makes him a rather dangerous criminal." ”